In recent years, portable terminal devices such as mobile telephones, PHSs (Personal Handyphone Systems), PDAs (Personal Data Assistance, Personal Digital Assistants: personal portable information communication devices), and the like, in which wireless communication is possible, include devices in which a PTT communication function is installed (for example, refer to Patent Documents 1 and 2).
Here, the PTT is a walkie-talkie type of device using IP (Internet Protocol), and conversation is one-way. Furthermore, with the PTT, parties being spoken to can be grouped, as in IM (Instant Messaging) and it is possible to view a state of the party to be spoken to (termed “another party”).
Therefore, in the PTT, it is possible to select another party (an individual or a group) who is in a conversation state, and press a conversation button (or a PTT button or the like) to speak. That is, the PTT is a transceiver mode for a portable telephone; there is no necessity to dial a number of another party, time to connect is short, and it is possible to converse with a plurality of locations simultaneously. In conversation in such cases, speech is transmitted all at once from an individual having a right to speak, to another party in a conversation state, and the other party in the conversation state receives and listens to the speech.
In the PTT, charges are often set lower than normal. Furthermore, in an operation procedure, a conversation partner list prepared separately from a normal telephone book is opened, selection of the other party is determined, and conversation takes place by pressing a conversation button (or a PTT button or the like). At this time, if a plurality of conversation partners is selected, conversation takes place with multiple locations.                [Patent Document 1] Japanese Patent Kohyo Publication No. JP-P2002-536928A        [Patent Document 2] Japanese Patent Kohyo Publication No. JP-P2003-526275A        